This invention relates to biofilm measurement and the efficacy of biocides on microbes.
Water processing systems including regenerative water processing systems are susceptible to formation of biofilm. Unless countermeasures are taken, microbes may colonize the interior surfaces and aqueous flow lines of these systems. Microbial biofilms can cause both process and health-related problems. Control or elimination of them is required to prevent adverse effects. Pathogenicity is of primary concern for human consumption, while additional concerns focus on the phytotoxic nature of bacterial contaminants.
Biofilm bacteria have been isolated from water lines and in potable water systems. These biofilms may harbor pathogens as well as microbial strains having resistance factors that could affect health. Therefore, delivery of potable hygienic water of acceptable quality is requisite for reliance upon water processing systems. Microbial contamination and biofilm development in water storage and distribution systems thus must be controlled possibly long periods of time.
Remediation methods are continually being sought to disinfect and remove biofilms from water lines. One proposed biocide (disinfection agent) for water systems is iodine. However, iodine may allow the development of resistant strains. For example, a four year test of a ground-based model of a spacecraft potable-water system showed that iodine treatment can limit planktonic microbes, but biofilms developed despite biocide treatment. Other tests have shown that increased resistance to disinfection results from attachment to or association of microbes with various surfaces of the water system.
Paramount to the treatment of biological depositions is the ability to monitor the microbial attachment process. Sessile organisms usually are monitored by either direct enumeration of viable bacteria, indirect enumeration using fluid frictional resistance measurements, colorimetric viability measurements, or electrical measurements. Other monitoring methods have also been employed.
Effective alternative remediation methods may, however, require a true understanding of colonization events and physiological factors that influence bacterial adhesion. This understanding may be aided by monitoring either adhesion or the effect of biocides on sessile bacteria continuously, without halting growth. Whether biofilm-control procedures are compatible with closed or open water processing environments is a primary consideration.
Unlike some water-treatment protocols, the use of toxic, potentially corrosive, or noxious chemicals may not be possible in closed environments. Other constraints may limit the types of chemicals and methods that can be used to treat water systems. These constraints may arise from limitations on space, power, and time. Further constraints may be imposed by other factors. For example, system design may dictate whether various chemicals can be used in the treatment system without adversely affecting the system itself.
Ideally, biocide/biofilm control agents should kill the target organism quickly and remove a wide variety of bacteria including spores and biological debris. In addition, the agents should not produce toxic residues or be harmful to the system itself. There may be no single chemical agent or procedure that meets these criteria at the present time. Several agents, each with specific biological-control capabilities, may, therefore, be required to do the job.
In general, in one aspect, the invention features an apparatus for monitoring particulate matter in a fluid container or conduit. The apparatus may include a wall portion that supports sessile particles derived from the fluid. The apparatus may also include means for forming images of the sessile particles and particles in the fluid adjacent the wall portion and means for digitizing and processing data corresponding to the images and for producing an output data segment corresponding to the sessile particles present in the images. The apparatus may further include means for processing the output data segment and deriving an output signal corresponding to the accumulation of sessile particles on the wall portion.
In general, in another aspect the invention features an apparatus for monitoring microbial matter within a fluid container. The apparatus may include a wall portion that supports sessile organisms derived from organisms present in the fluid. The apparatus may also include means for forming images of sessile organisms adhered to the wall portion and planktonic organisms in the fluid adjacent the wall portion and means for digitizing and processing data corresponding to the images and for producing an output data segment corresponding to the sessile organisms present in the images. The apparatus may further include means for processing the output data segment and deriving an output signal corresponding to the accumulation of sessile organisms on the wall portion.
In general, in another aspect, the invention features a method of monitoring particulate matter. The method may include supporting sessile particles derived from a fluid and forming images of the sessile particles and particles in the fluid adjacent the wall portion. The method may also include processing data corresponding to the images to produce an output data segment corresponding to the sessile particles present in the images and to derive an output signal corresponding to the accumulation of sessile particles.
In general, in another aspect, the invention features a method of monitoring microbial matter within a fluid container. The method may include supporting sessile organisms derived from organisms present in the fluid on a surface of the container and forming images of the sessile organisms adhered to the surface and planktonic organisms in the fluid adjacent the surface. The method may also include processing data corresponding to the images to produce an output data segment corresponding to the sessile organisms present in the images and to derive an output signal corresponding to the accumulation of sessile organisms on the surface of the container.
Implementations of the invention may also include one or more of the following: assessing the effect of an agent on sessile particles; and assessing the effect of biocide on sessile organisms.
Implementations of the invention may offer the advantage of processing liquids for the treatment of microbes without loss of water from a closed system.
Other features and advantages will become apparent from the following description, drawings, and from the claims.